Three times as likely to be obese at age 11 compared with wealthiest

Action Points

The impact of living in poverty on childhood obesity risk appears to increase as children age.

Note that poor diet, not getting regular exercise, irregular bedtimes, introduction of solid foods before age 4-months, and having a mother who smoked during pregnancy were all associated with higher obesity risk among the children in the study.

The impact of living in poverty on childhood obesity risk appears to increase as children age, according to findings from a major cohort study in the U.K.

At age 5, children living in poverty enrolled in the Millennium Cohort Study (MCS) were twice as likely as the most economically well-off children in the study to be obese. The gap widened over time, and by age 11 the obesity rate among the poorest children was three times higher than among the wealthiest.

Poor diet, not getting regular exercise, irregular bedtimes, introduction of solid foods before age 4-months, and having a mother who smoked during pregnancy were all associated with higher obesity risk among the children in the study, researcher Yvonne Kelly, of the University College London, and colleagues wrote in the European Journal of Public Health.

"All of these things have plausible biological pathways to explain their association with weight gain," Kelly told MedPage Today. "Sleep seemed to be strongly associated with weight. Getting enough sleep seemed to help protect normal weight kids from becoming overweight and overweight kids from becoming obese."

Kelly explained that while many earlier studies have linked living in poverty with increased obesity risk in children, few have followed children over time to examine whether this impact becomes greater as children get older.

"If we accept the premise that we live in an obesogenic environment, and that this is especially true for people living in poverty, it would make sense that the longer you spend in this environment the more likely you are to have excess weight gain," Kelly said.

The study included data on children participating in the MCS with data on key developmental factors, including weight, at age 5 and age 11. The study is tracking close to 20,000 families living all across the U.K., and the analysis included children born between September of 2000 to January of 2002.

At age 5, 15% of the children in the analysis were overweight and 5% were obese. At age 11, 20% of the children were overweight and 6% were obese.

Socioeconomic inequalities were measured using quintiles of family income. Diet, physical activity level, and maternal health behaviors were included in the analysis.

Unadjusted analysis showed dramatic income inequalities in the risk of obesity at ages 5 and 11.

"At age 5, children in the bottom income quintile had 2.0 (95% CI 1.4-2.8) increased relative risk of being obese whilst at age 11 they had 3.0 (95% CI 2.0-4.5) increased risk compared to children in the top income quintile," the researchers wrote. "Similar income inequalities in the risk of overweight emerged by age 11. Physical activity and diet were particularly important in explaining inequalities."

Specifically:

Skipping breakfast and eating fruit were risk factors for overweight and obesity at age 5, but they appeared to have a minor role at age 11.

Engaging in a sport more than three times a week appeared to be protective at age 11.

Having an irregular bedtime was more strongly associated with overweight and obesity at age 5 than age 11.

Introduction of solid foods before 4 months and mother's BMI were positively associated with weight gain across weight categories at both ages, while maternal smoking during pregnancy was significantly associated with weight gain at age 5, but not at age 11.

The findings further support the need to make early interventions available to children living in poverty, the researchers concluded.

"The magnitude of income inequalities in child obesity and overweight grew between ages 5 and 11," they wrote, adding that poorer children were more likely to experience upward movements across weight categories than more advantaged children.

"These findings suggest that efforts to curb the increasing prevalence of obesity, particularly amongst disadvantaged children, should start early in life," they wrote. "Intervening in the early years when the family environment has more profound influences on children's healthy development has the potential to be particularly effective - setting children onto 'healthy', or at least healthier, adiposity trajectories."

This research was funded by the U.K. Economic and Social Research Council's International Centre for Life Course Studies in Society and Health.

The researchers declared no relevant relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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